Modern industrial methods have resulted in a need for an apparatus that is capable of effeciently filtering high temperature combustion gases containing particulate material. In combustion turbine application, for example, a combustion turbine extracts energy from hot combustion gases produced by burning natural or propane gas, petroleum distillates or low ash fuel oil. The limitation to not use coal or other solid fuels is that the particular carry over from combustion of such solid fuels turbine blade erosion and fouling. An efficient system for filtering of such hot combustion gases would permit the use of such solid fuels. As another example, in conventional boiler operations, the boilers undergo routine shutdown for cleaning the fireside surfaces and for inspection. An efficient hot gas filtering system would greatly extend the life and operational time for a boiler to operate between inspections. Fouling of the fireside surface due to ash deposition and corrosion would be eliminated or minimized. These oxidizing, high temperature and high pressure gases are difficult to filter using conventional techniques.
Removal of particulates from a hot combustion gas can prolong the life of turbine buckets in combustion turbine-generator systems and minimize fouling of heat exchange surfaces or boiler tubes in fossil fuel and cogeneration plants. Governmental regulations on permissible emissions due to public health considerations also add urgency to the effort to provide an efficient system for filtering such hot combustion gases. In recent years, a considerable amount of development effort has been expended developing an alternative to conventional cyclone separators for control of particulates in high temperature combustion gases. The new technology extends low temperature filtration experience developed for many years in conventional bag house filter systems.
Examples of the effects of assignee of the present invention in meeting the needs for filtering of hot gases are given in the aboveidentified related applications. In the Israelson et al. application, Ser. No. 817,704 now abandoned, an apparatus and process are described for use in filtering a hot, corrosive gas stream, such as a zirconium tetrachloride gas stream, to remove particulates therefrom without condensate or solids forming in the filtered gas due to cooling of the gas prior to exhaust from the filter system. While that filter apparatus uses a tubesheet to divide a filter vessel, or housing, into two chambers, with hollow, tubular filter elements suspended thereby, and uses a flexible support means to connect a support plate of the tubesheet to the wall of the housing, and is exceptionally suited to filtering gaseous streams of zirconium tetrachloride at temperatures in excess of about 450.degree. C. (842.degree. F.), the same would not effectively operate at higher temperatures of up to about 900.degree. C. (1652.degree. F.) and high pressures, due to the stresses applied to the tubesheet and support under such extreme operational conditions, In the Ciliberti et al. application Ser. No. 932,115, an apparatus for filtering of high temperature gases is described, and the problem of sealing a hollow, ceramic, tubular filter element to a tubesheet, at temperatures in the range of 700.degree.-900.degree. C. (1292.degree.-1652.degree. F.), discussed, with the use of a spiral ceramic spring made to bias the filter element to a tubesheet. As mentioned therein, metallic spring elements display a sharp drop in modulus of elasticity and become soft and yielding at temperatures in the range of 700.degree.-900.degree. C., and such temperatures also effect the properties of other metallic components of filtering systems.
It is an object of the present invention to provide a filtering apparatus that is usable to filter high temperature, high pressure, aggressive gases, such as oxidizing gases.